Sometimes you might need to take an App down if an issue arises or bug has been discovered that you need some time to investigate.
On the Deployment Tab, I would like to see a toggle to take the live app version offline, and also a field to set which page is used to display when offline. When the App is toggled ‘offline’ all page requests are served the selected offline maintenance page.
This would also in effect would be the page displayed during any deployment periods which you could, so prior to an upgrade, if you wish, you could take the App offline, perform the upgrade, the put the app back online.
The page would be the same as any other where the users can add the content that states the site is offline for maintenance, provide an email contact address etc. etc.